1. Field of the Invention
This invention relates in general to a protection of magnetoresistive heads, and more particularly to a method and apparatus for providing electrostatic discharge protection of a magnetic head using a mechanical switch and an electrostatic discharge device network.
2. Description of Related Art
Most disc drives built today use conventional thin-film recording heads. Magnetic heads typically consist of a titanium carbide ceramic or silicon slider body and a transducer. Today, most disk drives employ MR heads. MR heads provide improved performance in a number of important respects.
MR heads operate on according to a phenomenon known as the magneto-resistive effect. Certain metals, when exposed to a magnetic field, change their resistance to the flow of electricity. This property is exploited in creating the read element of an MR head. Reading information for the media is accomplished by constantly passing a sense current through the read element of the head. When the head passes over a magnetic field on the media, the head changes its resistance, which is detected by the change in amperage of the sense current.
A major problem that is found during the manufacture of magnetic recording heads, particularly of the thin film type, is the spurious discharge of static electricity which has been undesirably generated. Static charges may be produced by the presence of certain materials, such as plastics, which are present in the surroundings at the place of manufacture of the magnetic heads. Further, static charges may be present during human handling and tooling of the magnetic recording heads. Compared to previous generation thin-film heads, MR heads are typically 200 times more sensitive to damage caused by electrostatic discharge (ESD)
When there is a static discharge, between a magnetic pole piece and an adjacent conductive layer, the pole piece may be damaged, particularly at a critical sensing portion, such as at the tip of the pole piece which is exposed and disposed adjacent to the transducing gap facing the record medium. In addition, the dielectric or insulating material that surrounds the magnetic head coil could break down from the discharge effect. As a result, the head assembly is subject to deterioration and degradation so that it is rendered virtually useless.
Approaches to alleviate this problem have involved the grounding of operators, table tops, or the use of ion producing fans and air hose nozzle application. Also, the materials used for storage containers and work trays must be carefully selected. However, the basic problem of spurious discharge at the critical pole tip area has not been completely solved by these approaches.
In addition, many approaches have been used for protecting magnetic heads from ESD destruction. For example, U.S. Pat. No. 5,710,682, issued Jan. 20, 1998, to Arya et al., entitled xe2x80x9cELECTROSTATIC DISCHARGE PROTECTION SYSTEM FOR MR HEADSxe2x80x9d, and incorporated herein by reference, discloses a shorting bar, which comprises an electrically conductive member attached to the actuator arm, for automatically connecting the MR wire leads at an exposed contact region of the MR head wire leads when absence of support of the MR head permits the load beam to bend sufficiently toward the shorting bar. However, the shorting of the leads by the shorting bar prevents testing and other diagnosis of the MR head.
It can be seen that there is a need for a method and apparatus for providing electrostatic discharge protection of a magnetic head without preventing electrostatic discharge testing or other diagnosis of the magnetic head.
It can also be seen that there is a need for a method and apparatus for providing electrostatic discharge protection of a magnetic head using a mechanical switch and an electrostatic discharge device network.
To overcome the limitations in the prior art described above, and to overcome other limitations that will become apparent upon reading and understanding the present specification, the present invention discloses a method and apparatus for providing electrostatic discharge protection of a magnetic head using a mechanical switch and an electrostatic discharge device network.
The present invention solves the above-described problems by providing a mechanical switch that is in series and parallel configuration with a silicon electrostatic discharge network. The electrostatic discharge network can be controlled in an on or off state for testing, evaluation or diagnostics of the armature or MR head.
A method in accordance with the principles of the present invention includes engaging an electrostatic discharge element between leads from a head element in response to absence of support to the head.
Other embodiments of a method in accordance with the principles of the invention may include alternative or optional additional aspects. One such aspect of the present invention is that the method further includes disengaging the electrostatic discharge element in response to support being applied to the head.
Another aspect of the present invention is that the electrostatic discharge element is turned on to maintain electrostatic discharge protection for the head.
Another aspect of the present invention is that the electrostatic discharge element is turned off to allow operation of the head.
Another aspect of the present invention is that the operation of the head includes testing, evaluation and diagnostics of the head.
Another aspect of the present invention is that the electrostatic discharge element is coupled to a first lead from a head element via a first input/output line, the engaging further including shorting a second lead from the head element to a second input/output line of the electrostatic discharge element.
Another aspect of the present invention is that the shorting connects the electrostatic discharge element being to the first and second leads from the head element in parallel with the head element.
Another aspect of the present invention is that the electrostatic discharge element includes a pair of back-to-back, parallel diodes for accommodating both positive and negative potentials across the element.
Another aspect of the present invention is that the electrostatic discharge element includes an N-type MOSFET transistor disposed between the first and second lead of the head element, a gate of the MOSFET transistor being tied to the first lead of the head element.
Another aspect of the present invention is that the head element includes an MR element.
Another aspect of the present invention is that the head element includes an inductive coil element.
Another embodiment of the present invention includes an apparatus for protecting an MR head from electrostatic discharge, wherein the apparatus includes a first lead from a head element, a second lead from a head element having a contact point, an electrostatic discharge element, coupled to the first lead from the head element via a first input/output line, the electrostatic discharge element having a second input/output line with a contact point and a conductive member positioned proximate the contact point of the second lead and the contact point of the second input/output line, the conductive member engaging the contact point of the second lead and the contact point of the second input/output line in response to absence of support to the head, the engagement of the conductive member with the contact point of the second lead and the contact point of the second input/output line connecting the electrostatic discharge element to the first and second leads from the head element in parallel with the head element.
Another embodiment of the present invention includes a disk drive system, wherein the disk drive includes a magnetic storage disk for storing data thereon, a MR head located proximate to the disk for reading and writing data to and from the disk, a disk movement device, coupled to the disk, for rotating the disk, an actuator arm, coupled to the MR head, for supporting the MR head and an actuator, coupled to the access arm, for moving actuator arm to position the MR head relative to the disk; wherein the actuator arm further includes a first lead from a head element, a second lead from a head element having a contact point, an electrostatic discharge element, coupled to the first lead from the head element via a first input/output line, the electrostatic discharge element having a second input/output line with a contact point, and a conductive member positioned proximate the contact point of the second lead and the contact point of the second input/output line, the conductive member engaging the contact point of the second lead and the contact point of the second input/output line in response to absence of support to the head, the engagement of the conductive member with the contact point of the second lead and the contact point of the second input/output line connecting the electrostatic discharge element to the first and second leads from the head element in parallel with the head element.